// @file file_allocator.h

/*    Copyright 2009 10gen Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the GNU Affero General Public License in all respects
 *    for all of the code used other than as permitted herein. If you modify
 *    file(s) with this exception, you may extend this exception to your
 *    version of the file(s), but you are not obligated to do so. If you do not
 *    wish to do so, delete this exception statement from your version. If you
 *    delete this exception statement from all source files in the program,
 *    then also delete it in the license file.
 */

#include "mongo/pch.h"

#include <list>
#include <boost/filesystem/path.hpp>
#include <boost/thread/condition.hpp>

#include "mongo/util/concurrency/mutex.h"

namespace mongo {

    /*
     * Handles allocation of contiguous files on disk.  Allocation may be
     * requested asynchronously or synchronously.
     * singleton
     */
    class FileAllocator : boost::noncopyable {
        /*
         * The public functions may not be called concurrently.  The allocation
         * functions may be called multiple times per file, but only the first
         * size specified per file will be used.
        */
    public:
        void start();

        /**
         * May be called if file exists. If file exists, or its allocation has
         *  been requested, size is updated to match existing file size.
         */
        void requestAllocation( const std::string &name, long &size );


        /**
         * Returns when file has been allocated.  If file exists, size is
         * updated to match existing file size.
         */
        void allocateAsap( const std::string &name, unsigned long long &size );

        void waitUntilFinished() const;

        static void ensureLength(int fd, long size);

        /** @return the singleton */
        static FileAllocator * get();
        
    private:

        FileAllocator();

        void checkFailure();

        // caller must hold pendingMutex_ lock.  Returns size if allocated or
        // allocation requested, -1 otherwise.
        long prevSize( const std::string &name ) const;

        // caller must hold pendingMutex_ lock.
        bool inProgress( const std::string &name ) const;

        /** called from the worked thread */
        static void run( FileAllocator * fa );

        // generate a unique name for temporary files
        std::string makeTempFileName( boost::filesystem::path root );

        mutable mongo::mutex _pendingMutex;
        mutable boost::condition _pendingUpdated;

        std::list< std::string > _pending;
        mutable std::map< std::string, long > _pendingSize;

        // unique number for temporary files
        static unsigned long long _uniqueNumber;

        bool _failed;

        static FileAllocator* _instance;

    };

} // namespace mongo
